Whip the cream and chill. Roughly chop the chocolate and melt over steam. At the same time, mix the eggs with the yolk and vanilla sugar over a second water bath and beat until frothy. Take the bowl off the steam, place it in a cold water bath and stir the cream until it has cooled down again. Stir melted chocolate into the yolk mixture, mix in the liqueur and carefully fold in the cream. Fill the cream into glasses and place in the refrigerator for approx. 3 hours to set.